TRANSFORMER DAMAGE

[arvinolga]

Hi!

Two of our customer's transformer got damaged (one on the primary side and the other one exploded). The transformer is a 13.8kV/480V (the other 415V)oil immersed type. Both the winding's primary side were reading zero on all phase to phase. What can be the cause of such failure if the overvoltage from the utility is not the factor?

 

[Nick]

Re: TRANSFORMER DAMAGE

Reading 0 what phase to phase. Were the windings disconnected? What type of test was done. As far as what happened, when was the last time the transformer oil was tested? Were they leaking or was there a breach in the tank where moisture could get in?

 

[rcwilson]

Re: TRANSFORMER DAMAGE

Most utility transformers will read O ohms phase to phase on a megger. The windings are connecetd phase to phase and they are low resistance. A better test is to tie the HV windigns together and LV winsigns together and then meg HV to LV, HV to G and LV to ground.

Sounds like a lightning strike or a voltage surge got to the transformers. Were there any surge arrestors on the primary?

 

[charlie]

Re: TRANSFORMER DAMAGE

Besides the normal testing and maintenance that has already been described, did you have properly sized lightning arresters (10 kV)?